Substrate treatment device and substrate treatment method

ABSTRACT

A substrate treatment device according to an embodiment includes a placement portion on which a substrate is placed and rotated, a liquid supply portion which supplies a liquid to a surface on an opposite side to the placement portion of the substrate, a cooling portion which supplies a cooling gas to a surface on a side of the placement portion of the substrate, and a control portion which controls at least one of a rotation speed of the substrate, a supply amount of the liquid, and a flow rate of the cooling gas. The control portion brings the liquid present on a surface of the substrate into a supercooled state and causes at least a part of the liquid brought into the supercooled state to freeze.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of U.S. patentapplication Ser. No. 15/671,529 filed on Aug. 8, 2017, which claimspriority from Japanese Patent Application No. 2016-156786, filed on Aug.9, 2016; the entire contents of which are incorporated herein byreference.

FIELD

Embodiments described herein relate generally to a substrate treatmentdevice and a substrate treatment method.

BACKGROUND

In a microstructure such as a template for imprinting, a mask substratefor photolithography, or a semiconductor wafer, a minute concave convexportion is formed on a surface of a substrate.

Here, as a method of removing a contaminant such as a particle adheredto the surface of the substrate, an ultrasonic cleaning method, atwo-fluid spray cleaning method, etc. are known. However, if anultrasonic wave is applied to the substrate or a fluid is sprayed ontothe surface of the substrate, the minute concave convex portion formedon the surface of the substrate may be damaged. Further, recently,miniaturization of the concave convex portion has progressed, and theconcave convex portion is more likely to be damaged.

Therefore, as a method of removing a contaminant adhered to the surfaceof the substrate, a freeze cleaning method has been proposed.

In the freeze cleaning method, first, pure water is supplied to thesurface of the rotated substrate, and a part of the supplied pure wateris discharged to form a water film on the surface of the substrate.Subsequently, a cooling gas is supplied to the substrate on a side wherethe water film is formed to freeze the water film. When the water filmis frozen and an ice film is formed, the contaminant is incorporatedinto the ice film, and therefore, the contaminant is separated from thesurface of the substrate. Subsequently, pure water is supplied to theice film to thaw the ice film, and the contaminant is removed from thesurface of the substrate along with the pure water.

According to the freeze cleaning method, the minute concave convexportion formed on the surface of the substrate can be prevented frombeing damaged.

However, when the cooling gas is supplied to the substrate on a sidewhere the water film is formed, freezing starts from a side of thesurface of the water film (on an opposite side to the substrate of thewater film). When freezing starts from the side of the surface of thewater film, it becomes difficult to separate an impurity adhered to thesurface of the substrate from the surface of the substrate. Therefore,it was difficult to improve a contaminant removal efficiency.

SUMMARY

A substrate treatment device according to an embodiment includes aplacement portion on which a substrate is placed and rotated, a liquidsupply portion which supplies a liquid to a surface on an opposite sideto the placement portion of the substrate, a cooling portion whichsupplies a cooling gas to a surface on a side of the placement portionof the substrate, and a control portion which controls at least one of arotation speed of the substrate, a supply amount of the liquid, and aflow rate of the cooling gas. The control portion brings the liquidpresent on a surface of the substrate into a supercooled state andcauses at least a part of the liquid brought into the supercooled stateto freeze.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view for illustrating a substrate treatment deviceaccording to the embodiment;

FIG. 2 is a timing chart for illustrating the substrate treatment methodaccording to the embodiment;

FIG. 3 is a graph for illustrating a case where only the supercoolingprocess was performed, and a case where the supercooling process and thefreezing process were performed;

FIG. 4 is a graph for illustrating a relationship between thetemperature of the liquid in the supercooling process and the volumeexpansion coefficient in the freezing process;

FIG. 5 is a graph for illustrating a case where the process of supplyingthe liquid, the supercooling process, and the freezing process arerepeated a plurality of times; and

FIG. 6 is a schematic view for illustrating a substrate treatment device1 a according to another embodiment.

DETAILED DESCRIPTION

Embodiments will now be described with reference to the drawings.Similar components in the drawings are marked with like referencenumerals, and a detailed description is omitted as appropriate.

The substrate 100 exemplified below can be, for example, a semiconductorwafer, an imprint template, a mask substrate for photolithography, aplate-like body used for MEMS (Micro Electro Mechanical Systems), andthe like.

However, the application of the substrate 100 is not limited to these.

FIG. 1 is a schematic view for illustrating a substrate treatment device1 according to the embodiment.

As shown in FIG. 1, in the substrate treatment device 1, a placementportion 2, a cooling portion 3, a first liquid supply portion 4, asecond liquid supply portion 5, a housing 6, an air blowing portion 7, ameasurement portion 8, a control portion 9, and an exhaust portion 11are provided.

The placement portion 2 has a placement table 2 a, a rotation shaft 2 b,and a drive portion 2 c.

The placement table 2 a is provided inside the housing 6. The placementtable 2 a has a plate shape.

On one major surface of the placement table 2 a, a plurality ofprojection portions 2 a 1 for holding a substrate 100 is provided. Onthe plurality of projection portions 2 a 1, the substrate 100 is placed.When the substrate 100 is placed, a surface on a side where a concaveconvex portion is formed of the substrate 100 is made to face on anopposite side to the placement table 2 a. The concave convex portion canbe, for example, a pattern. The plurality of projection portions 2 a 1holds a periphery of the substrate 100. By allowing the plurality ofprojection portions 2 a 1 to hold a periphery of the substrate 100, aportion where the substrate 100 and an element on a side of theplacement table 2 a come into contact with each other can be reduced.Therefore, contamination, damage, or the like of the substrate 100 canbe suppressed.

In a central portion of the placement table 2 a, a hole 2 a 2penetrating in a thickness direction of the placement table 2 a isprovided.

One end portion of the rotation shaft 2 b is engaged in the hole 2 a 2of the placement table 2 a. The other end portion of the rotation shaft2 b is provided outside the housing 6. The rotation shaft 2 b isconnected to the drive portion 2 c outside the housing 6.

The rotation shaft 2 b has a cylindrical shape.

In an end portion on a side of the placement table 2 a of the rotationshaft 2 b, a blow-out portion 2 b 1 is provided. The blow-out portion 2b 1 opens to a surface on which the plurality of projection portions 2 a1 is provided of the placement table 2 a. An end portion on a side ofthe opening of the blow-out portion 2 b 1 is connected to an inner wallof the hole 2 a 2. The opening of the blow-out portion 2 b 1 faces asurface of the substrate 100 placed on the placement table 2 a.

The blow-out portion 2 b 1 has a shape such that a sectional areaincreases toward a side of the placement table 2 a (a side of theopening). Therefore, an inner hole of the blow-out portion 2 b 1 has ashape such that a sectional area increases toward a side of theplacement table 2 a (a side of the opening).

Incidentally, a case where the blow-out portion 2 b 1 is provided at atip of the rotation shaft 2 b is illustrated, however, the blow-outportion 2 b 1 can also be provided at a tip of a cooling nozzle 3 d.Further, the hole 2 a 2 of the placement table 2 a can also be made tofunction as the blow-out portion 2 b 1.

By providing the blow-out portion 2 b 1, a released cooling gas 3 a 1can be supplied to a wider region on a side of the placement table 2 aof the substrate 100. Further, a release speed of the cooling gas 3 a 1can be decreased. Therefore, the substrate 100 can be prevented frombeing partially cooled, or the cooling speed of the substrate 100 can beprevented from being too high.

As a result, the below-mentioned liquid 101 can be easily brought into asupercooled state. In addition, the liquid 101 can be brought into asupercooled state in a wider region of the substrate 100. Therefore, thecontaminant removal efficiency can be improved.

An end portion on an opposite side to the placement table 2 a of therotation shaft 2 b is closed. Into the end portion on the opposite sideto the placement table 2 a of the rotation shaft 2 b, the cooling nozzle3 d is inserted. Between the end portion on the opposite side to theplacement table 2 a of the rotation shaft 2 b and the cooling nozzle 3d, a rotation shaft seal (not shown) is provided. Therefore, the endportion on the opposite side to the placement table 2 a of the rotationshaft 2 b is sealed hermetically, and also fixed.

The drive portion 2 c is provided outside the housing 6. The driveportion 2 c is connected to the rotation shaft 2 b. The drive portion 2c can be configured to have a rotating device such as a motor. Arotational force of the drive portion 2 c is transmitted to theplacement table 2 a through the rotation shaft 2 b. Therefore, by thedrive portion 2 c, not only the placement table 2 a, but also thesubstrate 100 placed on the placement table 2 a can be rotated.

Further, the drive portion 2 c not only can start rotation and stoprotation, but also can change the number of rotations (rotation speed).The drive portion 2 c can include, for example, a control motor such asa servomotor.

The cooling portion 3 directly supplies the cooling gas 3 a 1 to asurface on an opposite side to a surface to which the liquid 101 issupplied (a surface on a side of the placement table 2 a) of thesubstrate 100.

The cooling portion 3 has a cooling liquid portion 3 a, a filter 3 b, aflow rate control portion 3 c, and the cooling nozzle 3 d.

The cooling liquid portion 3 a, the filter 3 b, and the flow ratecontrol portion 3 c are provided outside the housing 6.

The cooling liquid portion 3 a stores the cooling liquid and producesthe cooling gas 3 a 1.

The cooling liquid is a material obtained by liquefying the cooling gas3 a 1.

The cooling gas 3 a 1 is not particularly limited as long as it is a gaswhich hardly reacts with a material of the substrate 100.

The cooling gas 3 a 1 can be, for example, an inert gas such as nitrogengas, helium gas, or argon gas. In this case, by using a gas having ahigh specific heat, a cooling time for the substrate 100 can be reduced.For example, by using helium gas, a cooling time for the substrate 100can be reduced. Further, by using nitrogen gas, a treatment cost for thesubstrate 100 can be reduced.

The cooling liquid portion 3 a has a tank which stores the coolingliquid and a vaporization portion which vaporizes the cooling liquidstored in the tank. In the tank, a cooling device for maintaining thetemperature of the cooling liquid is provided. The vaporization portionproduces the cooling gas 3 a 1 from the cooling liquid by increasing thetemperature of the cooling liquid. The vaporization portion can be, forexample, a portion which utilizes an outside air temperature, or usesheating by a heating medium. The temperature of the cooling gas 3 a 1may be any temperature as long as the liquid 101 can be brought into asupercooled state by cooling the liquid 101 to a temperature not higherthan the solidifying point. Therefore, the temperature of the coolinggas 3 a 1 may be a temperature not higher than the solidifying point ofthe liquid 101, and the temperature of the cooling gas 3 a 1 can be setto, for example, −170° C.

The filter 3 b is connected to the cooling liquid portion 3 a through apipe. The filter 3 b prevents a contaminant such as a particle containedin the cooling liquid from flowing out to a side of the substrate 100.

The flow rate control portion 3 c is connected to the filter 3 b througha pipe.

The flow rate control portion 3 c controls a flow rate of the coolinggas 3 a 1. The flow rate control portion 3 c can be, for example, an MFC(Mass Flow Controller) or the like. Further, the flow rate controlportion 3 c may be a portion which indirectly controls a flow rate ofthe cooling gas 3 a 1 by controlling a supply pressure of the coolinggas 3 a 1. In this case, the flow rate control portion 3 c can be, forexample, an APC (Auto Pressure Controller) or the like.

The temperature of the cooling gas 3 a 1 produced from the coolingliquid in the cooling liquid portion 3 a is substantially apredetermined temperature. Due to this, the flow rate control portion 3c can control not only the temperature of the substrate 100, but alsothe temperature of the liquid 101 on the substrate 100 by controllingthe flow rate of the cooling gas 3 a 1. In this case, the flow ratecontrol portion 3 c brings the liquid 101 into a supercooled state inthe below-mentioned supercooling process by controlling the flow rate ofthe cooling gas 3 a 1.

One end portion of the cooling nozzle 3 d is connected to the flow ratecontrol portion 3 c. The other end portion of the cooling nozzle 3 d isprovided inside the rotation shaft 2 b. The other end portion of thecooling nozzle 3 d is located in a vicinity of an end portion on a sideof the flow rate control portion 3 c of the blow-out portion 2 b 1.

The cooling nozzle 3 d has a cylindrical shape. The cooling nozzle 3 dsupplies the cooling gas 3 a 1 whose flow rate is controlled by the flowrate control portion 3 c to the substrate 100. The cooling gas 3 a 1released from the cooling nozzle 3 d is directly supplied to a surfaceon an opposite side to a surface to which the liquid 101 is supplied ofthe substrate 100 through the blow-out portion 2 b 1.

The first liquid supply portion 4 supplies the liquid 101 to a surfaceon an opposite side to the placement table 2 a of the substrate 100.

In the below-mentioned freezing process, when the liquid 101 is changedfrom a liquid to a solid (liquid-solid phase change), the volume ischanged, and therefore, a pressure wave is generated. It is consideredthat by this pressure wave, a contaminant adhered to the surface of thesubstrate 100 is separated. Therefore, the liquid 101 is notparticularly limited as long as it hardly reacts with a material of thesubstrate 100.

However, it is also considered that when a liquid whose volume increasesat the time of freezing is used as the liquid 101, by utilizing aphysical force resulting from the increase in the volume, a contaminantadhered to the surface of the substrate 100 can be separated. Therefore,it is preferred to use a liquid which hardly reacts with the material ofthe substrate 100 and whose volume increases at the time of freezing asthe liquid 101. For example, the liquid 101 can be water (for example,pure water, ultrapure water, or the like), a liquid containing water asa main component, or the like.

The liquid containing water as a main component can be, for example, amixed liquid of water and an alcohol, a mixed liquid of water and anacidic solution, a mixed liquid of water and an alkaline solution, orthe like.

When a mixed liquid of water and an alcohol is used, a surface tensioncan be decreased, and therefore, the liquid 101 can be easily suppliedto the inside of the minute concave convex portion formed on the surfaceof the substrate.

When a mixed liquid of water and an acidic solution is used, acontaminant such as a particle or a resist residue adhered to thesurface of the substrate 100 can be dissolved. For example, when a mixedliquid of water and sulfuric acid or the like is used, a contaminantcomposed of a resist or a metal can be dissolved.

When a mixed liquid of water and an alkaline solution is used, a zetapotential can be decreased, and therefore, a contaminant which isseparated from the surface of the substrate 100 can be prevented frombeing adhered to the surface of the substrate 100 again.

However, if rest of a component other than water is too much, it becomesdifficult to utilize a physical force resulting from the increase in thevolume, and therefore, the contaminant removal efficiency may bedecreased. Therefore, the concentration of the component other thanwater is preferably set to 5 wt % or more and 30 wt % or less.

Further, in the liquid 101, a gas can be dissolved. The gas can be, forexample, carbon dioxide gas, ozone gas, hydrogen gas, or the like.

When carbon dioxide gas is dissolved in the liquid 101, a conductivityof the liquid 101 can be increased, and therefore, electrificationremoval or electrification prevention of the substrate 100 can beperformed.

By dissolving ozone gas in the liquid 101, a contaminant composed of anorganic material can be dissolved.

The first liquid supply portion 4 has a liquid storage portion 4 a, asupply portion 4 b, a flow rate control portion 4 c, and a liquid nozzle4 d.

The liquid storage portion 4 a, the supply portion 4 b, and the flowrate control portion 4 c are provided outside the housing 6.

The liquid storage portion 4 a stores the liquid 101.

The supply portion 4 b is connected to the liquid storage portion 4 athrough a pipe. The supply portion 4 b supplies the liquid 101 stored inthe liquid storage portion 4 a to the liquid nozzle 4 d. The supplyportion 4 b can be, for example, a pump or the like having resistance tothe liquid 101. Incidentally, a case where the supply portion 4 b is apump is illustrated, however, the supply portion 4 b is not limited tothe pump. For example, the supply portion 4 b can be configured tosupply a gas into the liquid storage portion 4 a so as to press-feed theliquid 101 stored in the liquid storage portion 4 a.

The flow rate control portion 4 c is connected to the supply portion 4 bthrough a pipe. The flow rate control portion 4 c controls a flow rateof the liquid 101 supplied from the supply portion 4 b. The flow ratecontrol portion 4 c can be, for example, a flow rate control valve.

Further, the flow rate control portion 4 c also performs start and stopof the supply of the liquid 101.

The liquid nozzle 4 d is provided inside the housing 6. The liquidnozzle 4 d has a cylindrical shape. One end portion of the liquid nozzle4 d is connected to the flow rate control portion 4 c through a pipe.The other end portion of the liquid nozzle 4 d faces a surface on whichthe concave convex portion is formed of the substrate 100 placed on theplacement table 2 a. Therefore, the liquid 101 ejected from the liquidnozzle 4 d is supplied to the surface on which the concave convexportion is formed of the substrate 100.

Further, the other end portion (an ejection port for ejecting the liquid101) of the liquid nozzle 4 d is located nearly at a center of a regionwhere the concave convex portion of the substrate 100 is formed. Theliquid 101 ejected from the liquid nozzle 4 d spreads from the center ofthe region where the concave convex portion of the substrate 100 isformed, and a liquid film having a fixed thickness is formed on thesubstrate.

The second liquid supply portion 5 supplies a liquid 102 to a surface onan opposite side to the placement table 2 a of the substrate 100.

The second liquid supply portion 5 has a liquid storage portion 5 a, asupply portion 5 b, a flow rate control portion 5 c, and the liquidnozzle 4 d.

The liquid 102 is used in the below-mentioned thawing process.Therefore, the liquid 102 is not particularly limited as long as ithardly reacts with the material of the substrate 100 and hardly remainson the substrate 100 in the below-mentioned drying process. The liquid102 can be, for example, water (for example, pure water, ultrapurewater, or the like), a mixed liquid of water and an alcohol, or thelike.

The liquid storage portion 5 a can be configured in the same manner asthe liquid storage portion 4 a described above.

The supply portion 5 b can be configured in the same manner as thesupply portion 4 b described above. The flow rate control portion 5 ccan be configured in the same manner as the flow rate control portion 4c described above.

Incidentally, in the case where the liquid 102 and the liquid 101 arethe same, the second liquid supply portion 5 can be omitted. Further, acase where the liquid nozzle 4 d is shared is illustrated, however, itis also possible to separately provide a liquid nozzle which ejects theliquid 101 and a liquid nozzle which ejects the liquid 102.

Further, the temperature of the liquid 101 can be set to a highertemperature than the solidifying point of the liquid 101. Thetemperature of the liquid 101 can be set to, for example, about normaltemperature (20° C.). Further, the temperature of the liquid 102 can beset to a temperature at which the frozen liquid 101 can be thawed. Thetemperature of the liquid 102 can be set to, for example, about normaltemperature (20° C.).

The housing 6 has a box shape.

In the housing 6, a cover 6 a is provided. The cover 6 a is supplied tothe substrate 100 and catches the liquid 101 supplied to the substrate100 and discharged to the outside of the substrate 100 by rotating thesubstrate 100. The cover 6 a has a cylindrical shape. An end portion (anend portion on an upper side in FIG. 1) on an opposite side to theplacement table 2 a of the cover 6 a is curved toward the center of thecover 6 a. Therefore, the liquid 101 scattered above the substrate 100can be easily captured.

Further, in the housing 6, a partition plate 6 b is provided. Thepartition plate 6 b is provided between an outer surface of the cover 6a and an inner surface of the housing 6.

On a side surface on a side of a bottom surface of the housing 6, adischarge port 6 c is provided. The used cooling gas 3 a 1, air 7 a, theliquid 101, and the liquid 102 are discharged to the outside of thehousing 6 from the discharge port 6 c.

To the discharge port 6 c, a discharge pipe 6 c 1 is connected, and tothe discharge pipe 6 c 1, the exhaust portion (pump) 11 which exhauststhe used cooling gas 3 a 1 and the air 7 a is connected. Further, to thedischarge port 6 c, also a discharge pipe 6 c 2 which discharges theliquids 101 and 102 is connected.

The discharge port 6 c is provided below the substrate 100. Therefore,by exhausting the cooling gas 3 a 1 from the discharge port 6 c, adownflow is formed. As a result, it is possible to prevent a particlefrom being whirled up.

In FIG. 1 and the below-mentioned FIG. 6, when the housing 6 is viewedin plan view, the discharge port 6 c is provided so that it is symmetricwith respect to the center of the housing 6. In the case of FIG. 1, twodischarge ports 6 c are provided. Therefore, the flow of the cooling gassymmetric with respect to the center of the housing 6 can be formed.Then, by making the flow of the cooling gas symmetric, uniform coolingon the surface of the substrate 100 can be achieved.

The air blowing portion 7 is provided on a surface of the ceiling of thehousing 6. Incidentally, the air blowing portion 7 can also be providedon a side surface on a side of the ceiling of the housing 6. The airblowing portion 7 can be configured to include a filter and an airblowing machine such as a fan. The filter can be, for example, an HEPAfilter (High Efficiency Particulate Air Filter) or the like.

The air blowing portion 7 supplies air 7 a (outside air) to a spacebetween the partition plate 6 b and the ceiling of the housing 6.Therefore, a pressure in the space between the partition plate 6 b andthe ceiling of the housing 6 is higher than an external pressure. As aresult, the air 7 a supplied by the air blowing portion 7 can be easilyguided to the discharge port 6 c. Further, a contaminant such as aparticle can be prevented from entering inside the housing 6 from thedischarge port 6 c.

Further, the air blowing portion 7 supplies the air 7 a at roomtemperature to a surface on an opposite side to the placement table 2 aof the substrate 100. Due to this, the air blowing portion 7 can changethe temperatures of the liquids 101 and 102 on the substrate 100 bycontrolling the supply amount of the air 7 a. Therefore, the air blowingportion 7 can control the supercooled state of the liquid 101 in thebelow-mentioned supercooling process, can promote freezing of the liquid101 in the freezing process, or can promote drying of the liquid 102 inthe drying process.

The measurement portion 8 is provided in the space between the partitionplate 6 b and the ceiling of the housing 6.

The measurement portion 8 can measure the temperature of the liquid 101on the substrate 100. In this case, the measurement portion 8 can be,for example, a radiation thermometer. Further, the measurement portion 8can be a measurement portion which measures the thickness of the liquid101 (the thickness of the liquid film) on the substrate 100. In thiscase, the measurement portion 8 can be, for example, a laserdisplacement meter, an ultrasonic displacement meter, or the like.

The measured temperature or thickness of the liquid 101 can be used forcontrolling the supercooled state of the liquid 101 in thebelow-mentioned supercooling process.

Incidentally, the “controlling the supercooled state” refers to anoperation in which the temperature change curve of the liquid 101 in asupercooled state is controlled so that the liquid 101 is not frozen dueto rapid cooling, in other words, the supercooled state is maintained.

The control portion 9 controls the operations of the respective elementsprovided in the substrate treatment device 1.

The control portion 9 controls, for example, the drive portion 2 c so asto change the number of rotations (rotation speed) of the substrate 100.

For example, the control portion 9 controls the rotation speed of thesubstrate 100 so as to make the supplied liquid 101 or liquid 102 spreadover the entire region of the substrate 100. The control portion 9controls the rotation speed of the substrate 100 so as to control thethickness of the liquid 101 on the substrate 100 or discharge the liquid101 or the liquid 102 from the substrate 100.

The control portion 9 controls, for example, the flow rate controlportion 3 c so as to change the flow rate of the cooling gas 3 a 1.

For example, the control portion 9 controls the flow rate of the coolinggas 3 a 1 so as to control the temperature or the cooling speed of theliquid 101. In this case, the control portion 9 can control not only theflow rate of the cooling gas 3 a 1, but also the temperature or thecooling speed of the liquid 101 based on the temperature of the liquid101 measured by the measurement portion 8.

Further, the cooling speed of the liquid 101 has a correlation with thethickness of the liquid 101 on the substrate 100. For example, as thethickness of the liquid 101 decreases, the cooling speed of the liquid101 increases. On the other hand, as the thickness of the liquid 101increases, the cooling speed of the liquid 101 decreases. Therefore, thecontrol portion 9 can control not only the flow rate of the cooling gas3 a 1, but also the cooling speed of the liquid 101 based on thethickness of the liquid 101 measured by the measurement portion 8.

Incidentally, the control of the temperature or the cooling speed of theliquid 101 is performed when the supercooled state of the liquid 101 iscontrolled in the below-mentioned supercooling process.

That is, the control portion 9 brings the liquid 101 on the surface ofthe substrate 100 into a supercooled state and causes at least a part ofthe liquid 101 brought into a supercooled state to freeze.

Incidentally, the “causing at least a part to freeze” may be performedsuch that at least a region covering the concave convex portion formedon the surface of the substrate 100 is frozen.

The control portion 9 causes execution of a series of processesincluding supplying the liquid 101, supercooling the liquid 101, andfreezing the liquid 101 a plurality of times.

The control portion 9 controls at least one of the rotation speed of thesubstrate 101 and the flow rate of the cooling gas 3 a 1 based on atleast one of the temperature of the liquid 101 and the thickness of theliquid 101 measured by the measurement portion 8.

Further, as described below, the control portion 9 controls at least oneof the flow rates of the cooling gas 3 a 1 and a gas 10 d with a highertemperature than the temperature of the cooling gas 3 a 1, and a mixingratio of the gas 10 d (see FIG. 6) to the cooling gas 3 a 1.

Next, along with the operation of the substrate treatment device 1, asubstrate treatment method according to the embodiment will beillustrated.

FIG. 2 is a timing chart for illustrating the substrate treatment methodaccording to the embodiment.

Incidentally, FIG. 2 shows a case where the substrate 100 is a 6025quartz (Qz) substrate (152 mm×152 mm×6.35 mm), and the liquid 101 ispure water.

First, the substrate 100 is carried in the housing 6 through acarry-in/carry-out port (not shown) of the housing 6.

The substrate 100 carried therein is placed on the plurality ofprojection portions 2 a 1 of the placement table 2 a and held thereon.

After the substrate 100 is placed and held on the placement table 2 a,as shown in FIG. 2, a freezing and cleaning process including apreliminary process, a cooling process (a supercooling process+afreezing process), a thawing process, and a drying process is performed.

First, as shown in FIG. 2, the preliminary process is executed.

In the preliminary process, the control portion 9 controls the supplyportion 4 b and the flow rate control portion 4 c so as to supply theliquid 101 at a predetermined flow rate to a surface on an opposite sideto the placement table 2 a of the substrate 100.

Further, the control portion 9 controls the flow rate control portion 3c so as to supply the cooling gas 3 a 1 at a predetermined flow rate toa surface on an opposite side to a surface to which the liquid 101 issupplied (a surface on a side of the placement table 2 a) of thesubstrate 100. Further, the control portion 9 controls the drive portion2 c so as to rotate the substrate 100 at a predetermined rotation speed(first rotation speed).

Here, when an atmosphere in the housing 6 is cooled by supplying thecooling gas 3 a 1 by the cooling portion 3, frost containing dust in theair is adhered to the substrate 100, which may become a cause ofcontamination. In the preliminary process, the liquid 101 iscontinuously supplied to the surface, and therefore, adhesion of frostto the surface of the substrate 100 can be prevented while uniformlycooling the substrate 100.

For example, in the case illustrated in FIG. 2, it is possible to setthe rotation speed of the substrate 100 to about 100 rpm, the flow rateof the liquid 101 to about 0.3 NL/min, the flow rate of the cooling gas3 a 1 to about 170 NL/min, and the process time of the preliminaryprocess to about 1800 sec.

Incidentally, this process time may be any time as long as the surfaceof the substrate 100 is uniformly cooled. Further, the temperature ofthe liquid 101 on the substrate 100 in this preliminary process issubstantially equal to the temperature of the liquid 101 to be suppliedbecause the liquid 101 is continuously supplied in a flowing state. Forexample, in the case where the temperature of the liquid 101 to besupplied is about normal temperature (20° C.), the temperature of theliquid 101 present on the substrate 100 (hereinafter referred to as“liquid film”) becomes about normal temperature (20° C.).

Subsequently, as shown in FIG. 2, the cooling process (supercoolingprocess+freezing process) is executed.

Incidentally, in this embodiment, in the cooling process, a process fromwhen the liquid 101 is brought into a supercooled state to when theliquid 101 starts to freeze is referred to as “supercooling process”,and a process from when the liquid 101 in a supercooled state is broughtinto a frozen state to when the liquid 101 starts to thaw in the thawingprocess is referred to as “freezing process”.

Here, when the cooling speed of the liquid 101 is too high, the liquid101 is not brought into a supercooled state, and is frozen immediately.

Therefore, the control portion 9 controls at least one of the flow rateof the cooling gas 3 a 1 and the rotation speed of the substrate 100 soas to bring the liquid 101 on the substrate 100 into a supercooledstate.

In the cooling process (supercooling process+freezing process), asillustrated in FIG. 2, supply of the liquid 101 supplied in thepreliminary process is stopped, and the rotation speed of the substrate100 is set to about 30 rpm. This rotation speed is a rotation speedallowing the liquid 101 supplied from the supply portion 4 b to spreadon the substrate 100 so as to form and maintain the liquid film having auniform thickness on the substrate 100. That is, the control portioncauses the substrate 100 to rotate at a rotation speed which is lowerthan the rotation speed during the preliminary process. Further, thethickness of the liquid film of the liquid 101 at this time can be madenot smaller than the height dimension of the concave convex portion.Further, the flow rate of the cooling gas 3 a 1 is maintained at 170NL/min.

In this manner, in the cooling process (supercooling process+freezingprocess), by stopping the supply of the liquid 101, the liquid on thesubstrate 100 stays and heat exchange is not performed. Further, bycontrolling the rotation speed of the substrate to become the secondrotation speed which is lower than the first rotation speed, the liquidon the substrate 100 stays and heat exchange is not performed.Therefore, by a cooling effect of the cooling gas 3 a 1 continuouslysupplied to the surface on a side of the placement table of thesubstrate 100, the temperature of the liquid film of the liquid 101 onthe substrate 100 is further decreased to a level lower than thetemperature of the liquid film during the preliminary process, andtherefore, the liquid 101 is brought into a supercooled state.

However, a condition for bringing the liquid 101 into a supercooledstate is affected by the size of the substrate 100, the viscosity of theliquid 101, the specific heat of the cooling gas 3 a 1, etc. Therefore,the condition for bringing the liquid 101 into a supercooled state ispreferably determined as appropriate by performing an experiment orsimulation.

In the freezing process, for example, by further decreasing thetemperature of the liquid 101, at least a part of the liquid 101 broughtinto a supercooled state is frozen. In the case illustrated in FIG. 2,when the temperature of the liquid 101 is decreased to about −30° C., atleast a part of the liquid 101 is frozen.

As described above, by stopping new supply of the liquid 101, andcontinuously supplying the cooling gas 3 a 1, the temperature of theliquid 101 is further decreased, and when the temperature of the liquid101 has reached a spontaneous freezing temperature, the liquid 101starts to freeze spontaneously.

However, a condition for freezing the liquid 101 brought into asupercooled state is not limited to the illustrated condition. Forexample, the flow rate of the cooling gas 3 a 1 may be increased.

Further, the liquid 101 may be frozen by applying vibration to theliquid 101 in a supercooled state or the like. In this case, it is alsopossible to provide an ultrasonic generator which applies vibration tothe liquid 101 on the substrate 100 directly or indirectly through therotation shaft 2 b or the like.

In this case, vibration may be applied based on the temperature of theliquid 101 measured by the measurement portion 8. For example, vibrationmay be applied when the temperature of the liquid 101 has reached apredetermined temperature. The predetermined temperature at this time isa temperature at which the volume expansion coefficient in the freezingprocess is large, and can be set to, for example, −35° C. or higher and−20° C. or lower. The temperature at which the volume expansioncoefficient in the freezing process is large will be described later.

Further, vibration may be applied by changing the rotation speed of thesubstrate 100 from the second rotation speed to a third rotation speed.

Subsequently, as shown in FIG. 2, the thawing process is executed.

Incidentally, the case illustrated in FIG. 2 is a case where the liquid101 and the liquid 102 are the same liquid. In FIG. 2, the liquid isshown as the liquid 101.

In the thawing process, the control portion 9 controls the supplyportion 4 b and the flow rate control portion 4 c so as to supply theliquid 101 at a predetermined flow rate to a surface on an opposite sideto the placement table 2 a of the substrate 100.

Incidentally, in the case where the liquid 101 and the liquid 102 aredifferent liquids, the control portion 9 controls the supply portion 5 band the flow rate control portion 5 c so as to supply the liquid 102 ata predetermined flow rate to a surface on an opposite side to theplacement table 2 a of the substrate 100.

Further, the control portion 9 controls the flow rate control portion 3c so as to stop the supply of the cooling gas 3 a 1. Further, thecontrol portion 9 controls the drive portion 2 c so as to increase therotation speed of the substrate 100. When the rotation of the substrate100 is faster, the liquid 101 and the frozen liquid 101 can be shakenoff by a centrifugal force and removed from the substrate 100.Therefore, it becomes easy to discharge the liquid 101 and the frozenliquid 101 from the substrate 100. Further, at this time, also acontaminant separated from the surface of the substrate 100 isdischarged from the substrate 100.

Incidentally, the supply amounts of the liquid 101 and the liquid 102are not particularly limited as long as thawing can be achieved.Further, the rotation speed of the substrate 100 is not particularlylimited as long as the liquid 101, the frozen liquid 101, and acontaminant can be discharged.

Subsequently, as shown in FIG. 2, the drying process is executed.

In the drying process, the control portion 9 controls the supply portion4 b and the flow rate control portion 4 c so as to stop the supply ofthe liquid 101.

Incidentally, in the case where the liquid 101 and the liquid 102 aredifferent liquids, the control portion 9 controls the supply portion 5 band the flow rate control portion 5 c so as to stop the supply of theliquid 102.

Further, the control portion 9 controls the drive portion 2 c so as tofurther increase the rotation speed of the substrate 100. When therotation of the substrate 100 is faster, the substrate 100 can be driedrapidly. Incidentally, the rotation speed of the substrate 100 is notparticularly limited as long as drying can be achieved.

In this manner, the treatment of the substrate 100 (removal of acontaminant) can be performed.

Next, the supercooling process and the freezing process will be furtherdescribed.

FIG. 3 is a graph for illustrating a case where only the supercoolingprocess was performed, and a case where the supercooling process and thefreezing process were performed. Incidentally, in the graph, a brokenline indicates the case where only supercooling was performed, and asolid line indicates the case where the supercooling process and thefreezing process were performed.

Further, as the temperature of the liquid film, the temperature of theliquid 101 in a supercooled state in the supercooling process is shown,and the temperature of a mixture of the liquid 101 and the frozen liquid101 in the freezing process is shown. Further, as shown in FIG. 3, inthe freezing process, the temperature of the mixture increases due tothe generated solidification heat.

As shown in FIG. 3, if the temperature of the liquid 101 is increasedbefore the liquid 101 is frozen, only the supercooling process can beperformed.

However, when only the supercooling process is performed, PRE (ParticleRemoval Efficiency) is decreased as compared with the case where thesupercooling process and the freezing process are performed. That is, achange in the volume of the liquid 101 does not occur when the freezingprocess is not performed, and therefore, a contaminant adhered to thesurface of the substrate 100 does not move or is not separated, andtherefore, the particle removal efficiency (contaminant removalefficiency) is decreased.

Incidentally, the PRE can be represented by the following formula whenthe number of particles before the treatment is represented by NI, andthe number of particles after the treatment is represented by NP.PRE (%)=((NI−NP)/NI)×100

The number of particles can be measured using a particle counter or thelike.

Due to this, in the substrate treatment method according to theembodiment, the freezing process is performed after the supercoolingprocess.

FIG. 4 is a graph for illustrating a relationship between thetemperature of the liquid 101 in the supercooling process and the volumeexpansion coefficient in the freezing process.

Incidentally, FIG. 4 shows a case where the liquid 101 is pure water.Further, in the freezing process, not all liquid 101 is frozen.Therefore, FIG. 4 shows a case where the liquid 101 and the frozenliquid 101 exist (a case where water and ice exist).

As shown in FIG. 4, in the case where the liquid 101 is pure water, thetemperature of the liquid 101 in the supercooling process is preferablyset to −35° C. or higher and −20° C. or lower.

By doing this, the volume expansion coefficient in the freezing processcan be increased. As described above, it is considered that in theseparation of a contaminant from the surface of the substrate 100, apressure wave resulting from a liquid-solid phase change and a physicalforce resulting from the increase in the volume are involved. Therefore,the temperature of the liquid 101 in a supercooled state is controlledto become a temperature at which the volume expansion coefficient in thefreezing process is large. That is, when the temperature of the liquid101 in the supercooling process is set to −35° C. or higher and −20° C.or lower, the contaminant removal efficiency can be improved.

Incidentally, a case where the liquid 101 is pure water is describedabove, however, the same applies to a case where the liquid 101 containswater as a main component. That is, if the liquid 101 contains water,the temperature of the liquid 101 in the supercooling process ispreferably set to −35° C. or higher and −20° C. or lower.

FIG. 5 is a graph for illustrating a case where the process of supplyingthe liquid 101, the supercooling process, and the freezing process arerepeated a plurality of times. Incidentally, FIG. 5 shows a case wherethe process of supplying the liquid 101, the supercooling process, andthe freezing process are performed 10 times.

Further, as shown in FIG. 5, when the process of supplying the liquid101 is provided after the freezing process (when the liquid 101 issupplied again), the temperature of the liquid film increases.Therefore, the supercooling process can be performed after the processof supplying the liquid 101. Further, the freezing process can beperformed after the supercooling process. Thereafter, in the same manneras above, a series of processes including the process of supplying theliquid 101, the supercooling process, and the freezing process can berepeated a plurality of times.

As described above, in the freezing process, not all liquid 101 isfrozen. That is, there may be a case where freezing does not occur insome region. However, in the embodiment, when a series of processesincluding the process of supplying the liquid 101, the supercoolingprocess, and the freezing process is repeated a plurality of times, theprobability of generation of a region where freezing does not occur canbe reduced. Therefore, the particle removal efficiency can be improved.

In the embodiment, the cooling gas 3 a 1 is supplied to a surface (backsurface) on a side of the placement table 2 a of the substrate 100 tocool the liquid 101 supplied on the surface of the substrate 100 andbring the liquid film into a supercooled state, and thereafter, theliquid film is frozen. According to this, the following effects areobtained.

When the cooling gas 3 a 1 is sprayed on the back surface of thesubstrate 100, that is, when the liquid film is cooled through thesubstrate 100, the liquid 101 is not blown off, and therefore, theliquid film can be frozen while maintaining the film thickness.Therefore, for example, as compared with the case where the cooling gas3 a 1 is sprayed from the surface of the substrate 100, local freezingdoes not occur. Due to this, the pressure applied between the concaveconvex portions provided on the surface of the substrate 100 can be madeuniform, and therefore, collapse of the concave convex portions due touneven freezing can be prevented.

Further, by cooling the liquid film of the liquid 101 supplied on thesurface of the substrate 100 to form the liquid film in a supercooledstate, and thereafter freezing the liquid film, the liquid film can befrozen while maintaining the thickness of the liquid film formed on thesurface of the substrate 100. Therefore, for example, as compared withthe case where the liquid brought into a supercooled state is suppliedin advance to the surface of the substrate 100, local freezing due toimpact of the supply of the liquid brought into a supercooled state ontothe substrate 100 does not occur. Due to this, the pressure appliedbetween the concave convex portions provided on the surface of thesubstrate 100 can be made uniform, and therefore, collapse of theconcave convex portions due to uneven freezing can be prevented.

Further, in the embodiment, cooling is achieved in the thicknessdirection from the back surface to the front surface of the substrate100. Therefore, even if a temperature gradient is present in thethickness direction of the liquid film of the liquid 101, in the liquidfilm of the liquid 101, the temperature of an interface between thesubstrate 100 and the liquid 101 (a surface on a side of the substrateof the liquid film) can be decreased to the lowest level. In this case,freezing starts from the interface between the substrate 100 and theliquid 101 (the surface on a side of the substrate of the liquid film).An adherend adhered to the substrate 100 mainly moves by expansion ofthe liquid 101 in a vicinity of the interface between the substrate andthe liquid 101 and is separated from the substrate, and therefore, theadherend adhered to the surface of the substrate 100 can be efficientlyseparated.

Further, when a part of the liquid film is frozen, freezing proceedsalso in the liquid film therearound by the impact wave or the formationof ice nuclei. Therefore, when the liquid 101 in a vicinity of theinterface is frozen, also the liquid 101 in a vicinity of the interfaceis frozen, however, in the liquid film of the liquid 101, thetemperature at which the liquid 101 in a vicinity of the interfacestarts to freeze can be decreased to the lowest level. As a result,expansion of the liquid 101 in a vicinity of the interface can beincreased.

An adherend adhered to the substrate 100 mainly moves by expansion ofthe liquid 101 in a vicinity of the interface between the substrate andthe liquid 101 and is separated from the substrate, and therefore, theadherend adhered to the surface of the substrate 100 can be efficientlyseparated.

Further, if cooling is performed using the cooling gas 3 a 1, it ispossible to perform cooling with high thermal responsiveness bycontrolling the flow rate. Therefore, when a temperature drop curve iscontrolled, rapid cooling of the liquid 101 can be suppressed. Further,the temperature until freezing can also be accurately controlled.

FIG. 6 is a schematic view for illustrating a substrate treatment device1 a according to another embodiment.

As shown in FIG. 6, in the substrate treatment device 1 a, a placementportion 2, a cooling portion 3, a first liquid supply portion 4, asecond liquid supply portion 5, a housing 6, an air blowing portion 7, ameasurement portion 8, a temperature measurement portion 8 a, a gassupply portion 10, and a control portion 9 are provided.

The temperature measurement portion 8 a measures the temperature in aspace between the substrate 100 and the placement table 2 a. Thistemperature is substantially equal to the temperature of a mixed gasobtained by mixing the cooling gas 3 a 1 and the gas 10 d flowingbetween the substrate 100 and the placement table 2 a.

The temperature measurement portion 8 a can be, for example, a radiationthermometer or the like.

The gas supply portion 10 has a gas storage portion 10 a, a flow ratecontrol portion 10 b, and a connecting portion 10 c.

The gas storage portion 10 a stores and supplies the gas 10 d. The gasstorage portion 10 a can be a high-pressure cylinder, a plant pipe, orthe like, in which the gas 10 d is contained.

The flow rate control portion 10 b controls the flow rate of the gas 10d. The flow rate control portion 10 b can be, for example, an MFC whichdirectly controls the flow rate of the gas 10 d or can be an APC whichindirectly controls the flow rate of the gas 10 d by controlling thepressure.

The connecting portion 10 c is connected to a rotation shaft 2 b. Theconnecting portion 10 c connects a space between the rotation shaft 2 band a cooling nozzle 3 d to the flow rate control portion 10 b. Theconnecting portion 10 c can be, for example, a rotary joint.

The gas 10 d is not particularly limited as long as it hardly reactswith a material of the substrate 100. The gas 10 d can be, for example,an inert gas such as nitrogen gas, helium gas, or argon gas. In thiscase, the gas 10 d can be the same gas as the cooling gas 3 a 1.

However, the temperature of the gas 10 d is higher than the temperatureof the cooling gas 3 a 1. The temperature of the gas 10 d can be set to,for example, room temperature.

As described above, if the cooling speed of a liquid 101 is too high,the liquid 101 is not brought into a supercooled state, and is frozenimmediately. That is, the supercooling process cannot be performed.

In this case, the cooling speed of the liquid 101 can be controlled byat least one of the flow rate of the cooling gas 3 a 1 and the rotationspeed of the substrate 100. However, the temperature of the cooling gas3 a 1 is substantially constant by setting the temperature in thecooling portion which supplies the cooling gas 3 a 1. Therefore, itsometimes becomes difficult to decrease the cooling speed of the liquid101 by the flow rate of the cooling gas 3 a 1.

Further, the cooling speed can be decreased by decreasing the rotationspeed of the substrate 100 so as to increase the thickness of the liquid101 on the substrate 100. However, there is a limit thickness retainedby the surface tension in the thickness of the liquid 101, andtherefore, it sometimes becomes difficult to decrease the cooling speedof the liquid 101 by the rotation speed of the substrate 100.

Therefore, in the embodiment, by mixing a gas 10 d with a highertemperature than the temperature of the cooling gas 3 a 1 with thecooling gas 3 a 1, the cooling speed of the liquid 101 can be decreased.The cooling speed of the liquid 101 can be controlled by the flow ratesof the gas 10 d and the cooling gas 3 a 1, the mixing ratio of the gas10 d to the cooling gas 3 a 1, the temperature of the gas 10 d, or thelike.

Further, even if the temperature of the liquid film of the liquid 101 onthe substrate 100 is detected by the measurement portion 8 and the flowrate of the cooling gas 3 a 1 is controlled, a difference sometimesoccurs between the temperature of the liquid film and the temperature ofthe surface (back surface) on a side of the placement table of thesubstrate 100 to be cooled. In this case, when the flow rate of thecooling gas 3 a 1 is controlled based only on the temperature of theliquid film detected by the measurement portion 8, even if thetemperature of the liquid film becomes an appropriate temperature, adifference occurs between the temperature of the liquid film and thetemperature of the back surface of the substrate 100, and a temperaturegradient in the thickness direction of the substrate 100 which greatlyaffects the freezing process is increased.

In this case, for example, in the process of treating a plurality ofsubstrates, for example, it becomes difficult to perform the sametemperature control for the Nth substrate and the N+1th substrate. Dueto this, unevenness occurs in the temperature curve of the supercooledstate for each substrate, and thus, a freezing timing for each substratemay differ.

However, in the embodiment, the control portion 9 can control at leastone of the flow rates of the gas 10 d and the cooling gas 3 a 1 and themixing ratio of the gas 10 d to the cooling gas 3 a 1 based on thetemperature measured by the temperature measurement portion 8 a.

The control portion 9 performs such control in the preliminary process,and can shift the process from the preliminary process to thesupercooling process (stop of the supply of the liquid 101) after thedifference between the temperature detected by the measurement portion 8and the temperature detected by the temperature measurement portion 8 adisappears.

Incidentally, a case where the flow rate control portion 3 c and the gassupply portion 10 are provided is illustrated, however, in the casewhere the gas supply portion 10 is provided, it is possible to adjustthe temperature of the cooling gas 3 a 1 by supplying the gas 10 d fromthe gas supply portion 10 without adjusting the flow rate of the coolinggas 3 a 1 by the flow rate control portion 3 c. Therefore, it is alsopossible to omit the flow rate control portion 3 c.

However, when the flow rate control portion 3 c and the gas supplyportion 10 are provided, the control of the supercooled state of theliquid 101 can be more easily performed.

Further, by controlling the amount of air 7 a supplied from the airblowing portion 7, it is also possible to control the supercooled stateof the liquid 101.

Hereinabove, embodiments are illustrated. However, the invention is notlimited to the description.

Those in which design change is appropriately added by a person skilledin the art with respect to the above-mentioned embodiments are alsoincluded in the scope of the invention as long as they include thefeatures of the invention.

For example, the shape, dimension, number, arrangement, and the like ofeach element included in the substrate treatment device 1 are notlimited to those illustrated and can be appropriately changed.

For example, in the above-mentioned embodiments, the substrate 100 iscooled by supplying the cooling gas 3 a 1 produced by vaporizing thecooling liquid in the cooling liquid portion 3 a to the substrate 100,however, the configuration is not limited thereto. For example, a gas atnormal temperature is cooled by chiller circulation, and the cooled gasmay be used as the cooling gas.

For example, in the above-mentioned embodiments, as shown in FIG. 2,when the process is shifted from the preliminary process to the coolingprocess, the rotation speed of the substrate 100 and the supply flowrate of the liquid 101 are changed simultaneously, however, theconfiguration is not limited thereto. For example, after the rotationspeed of the substrate 100 is changed from the first rotation speed tothe second rotation speed, the supply of the liquid 101 can be stopped.

For example, in the above-mentioned embodiments, as shown in FIG. 2, therotation speed in the cooling process (supercooling process+freezingprocess) is constant, however, the configuration is not limited thereto.For example, the rotation speed of the substrate 100 is set to thesecond rotation speed in the supercooling process, and thereafter canalso be changed to the third rotation speed which is larger (higher)than the second rotation speed in the freezing process. In this case,the liquid film on the substrate 100 can be made thin, and by increasingthe freezing speed, the treatment time can be reduced.

For example, in the above-mentioned embodiments, the thickness of theliquid film of the liquid 101 formed on the substrate 100 in the coolingprocess is set to not less than the height dimension of the concaveconvex portion, but may be a thickness allowing the liquid film to beformed along the shape of the concave convex portion on the side wallsurface and the surface of the concave convex portion. In this case, forexample, by setting the thickness of the liquid film to not more thanhalf the dimension of the concave convex portion, a space between theside wall surface and the side wall surface of the concave convexportion is not filled with the liquid film, and even if the liquid filmis frozen and expanded, a pressure is not applied to the concave convexportion, and thus, collapse of the concave convex portion can beprevented.

For example, in the above-mentioned embodiments, the supply of thecooling gas 3 a 1 by the cooling portion 3 is performed from below (on alower side in the gravitational direction) the substrate 100 to whichthe liquid 101 is supplied, however, the substrate 100 is held so as tomake the surface on which the concave convex portion is formed of thesubstrate 100 to which the liquid 101 is supplied face downward, and thesupply of the cooling gas 3 a 1 from the cooling portion 3 may beperformed from above the substrate 100. According to this configuration,in the drying process, discharge of the liquid component in the concaveportion on the surface of the substrate 100 can be accelerated by theforce of gravity.

Further, those in which addition, deletion, or design change of aconstituent element or addition, omission, or condition change of aprocess is appropriately made by a person skilled in the art withrespect to the above-mentioned embodiments are also included in thescope of the invention as long as they include the features of theinvention.

What is claimed is:
 1. A substrate treatment method, which comprises:rotating a substrate; supplying a liquid to one surface of thesubstrate; supplying a cooling gas to the other surface of thesubstrate; bringing the liquid present on the surface of the substrateinto a supercooled state by controlling at least one of a rotation speedof the substrate, a supply amount of the liquid, and a flow rate of thecooling gas; freezing at least a part of the liquid brought into thesupercooled state by controlling at least one of the rotation speed ofthe substrate, the supply amount of the liquid, and the flow rate of thecooling gas.
 2. The method according to claim 1, wherein in thesupplying the liquid and the supplying the cooling gas, the liquid issupplied to one surface of the substrate and the cooling gas is suppliedto the other surface of the substrate, and thereafter, in the bringingthe liquid into a supercooled state, the supply of the liquid is stoppedwhile maintaining the supply of the cooling gas so as to bring theliquid into a supercooled state.
 3. The method according to claim 1,wherein in the supplying the liquid, the substrate is rotated at a firstrotation speed, and in the bringing the liquid into a supercooled state,the substrate is rotated at a second rotation speed which is lower thanthe first rotation speed.
 4. The method according to claim 1, whereinthe supplying the liquid, the bringing the liquid into a supercooledstate, and the freezing at least a part of the liquid brought into thesupercooled state are executed a plurality of times.
 5. The methodaccording to claim 1, wherein the liquid contains water, and atemperature of the liquid brought into a supercooled state is −35° C. orhigher and −20° C. or lower.
 6. The method according to claim 1, whereinin the bringing the liquid into a supercooled state, at least one of atemperature of the liquid and a thickness of the liquid is measured, andat least one of a rotation speed of the substrate and a flow rate of thecooling gas is controlled based on at least one of the measuredtemperature of the liquid and the measured thickness of the liquid. 7.The method according to claim 1, wherein in the supplying the coolinggas, a gas with a higher temperature than a temperature of the coolinggas is mixed with the cooling gas, and in the bringing the liquid into asupercooled state, at least one of flow rates of the gas and the coolinggas and a mixing ratio of the gas to the cooling gas is controlled.